This invention relates in general to castor assemblies employing a self-laying track for supporting a frame or other structure to move over a floor or other surface.
Self-laying track castor assemblies have previously been provided. The Pat. to Lapham No. 2,810,151 discloses a castor which employs a disc journaled on a bearing block so as to turn and lay a track for a castor roller which is also journaled on the bearing block. The castor of the Lapham patent overcomes the problem of the relatively small diameter castor roller dropping into cracks or perforations as it is rolled along a floor. However, such a castor does not provide a smooth castoring action. Thus, for certain applications the castor resists movement or slips across the underlying floor, depending upon conditions such as the weight of the object being moved and the nature of the floor surface. In addition, the castor of Lapham is relatively complicated and expensive to construct in view of the fact that the parts do not lend themselves to fabrication by low cost plastic injection molding techniques.